// Nullish coalescing Operate
// 空值合并运算符
const b = 0
const a = b || 5
console.log(a) // 5

const b = false || null || ''
const a = b || 5
console.log(a) // 5

// 只判断 null and undefined

const b = 0
const a = b ?? 6 // ?? 只判断 null undefined  , false '' 0 判断为 true
console.log(a) // 0
